Effects of CGA-43089 on Responses of Sorghum (Sorghum Bicolor) to Metolachlor Combined by Ozone or Antioxidants

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Abstract
In greenhouse studies, the potential interactive effects of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] treatments combined with the air pollutant ozone (O3) or the antioxidants, piperonyl butoxide {α-[2-butoxyethyl) ethoxy]-4,5-dimethylenedioxy-2-propyltoluene} and n-propyl gallate, on the growth of sorghum [Sorghum bicolor (L.) Moench ‘Funk G522DR’] seedlings that were protected or unprotected with the antidote, CGA-43089 [α-(cyanomethoximino)-benzacetonitrile], were examined. Metolachlor was applied preplant incorporated at rates of 2.2, 3.9, and 5.6 kg/ha, and it was evaluated against fumigation with O3 at 0.2 and 0.3 ppmv or against 4.9, 6.7, and 9.0 kg/ha of each antioxidant applied preplant incorporated. In combination treatments, shoot dry weight at 30 days after planting was reduced more than expected by metolachlor in the presence of the protectant CGA-43089 and ozone or some rates of the two antioxidants, suggesting synergism. In the absence of the protectant, CGA-43089, growth responses of sorghum to combination treatments of metolachlor with ozone or propyl gallate suggested an additive effect, although some treatments of metolachlor combined with piperonyl butoxide interacted synergistically.